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African Journal of Basic & Applied Sciences 6 (1): 01-05, 2014ISSN 2079-2034© IDOSI Publications, 2014DOI: 10.5829/idosi.ajbas.2014.6.1.83324

Corresponding Author: Mansour Ziaei, Faculty Member of Occupational Health Department and Research Center forEnvironmental Determinants of Health (RCEDH), Kermanshah University of Medical Sciences,Kermanshah, Iran.

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Comparing of HAZOP and ETBA Techniques in Safety Risk Assessment at Gasoline Refinery Industry

Shirazeh Arghami, Sedigheh Abbasi, Shakiba Bakhtom and Mansour Ziaei1 2 2 3

Faculty Member of Occupational Health Department, Zanjan University of Medical Sciences, Zanjan, Iran1

Bachelor of Occupational Health Department, Zanjan University of Medical Sciences, Zanjan, Iran2

Faculty Member of Occupational Health Department and Research Center for Environmental Determinants3

of Health (RCEDH), Kermanshah University of Medical Sciences, Kermanshah, Iran

Abstract: Incidents prevention is very important in process industries, which requires detecting the hazard andrisk assessment. The aim of this cross-sectional study was to compare the HAZOP and ETBA techniques forsafety risk assessment in a gasoline refinery industry. Data was collected by PFD, P and ID, Walking-Talkingand direct observations. The worksheets of both HAZOP and ETBA techniques were filled based on MIL-STD-882E. HAZOP method detected 44 deviations were detected that 47.73% of them were unacceptable andundesirable, also 118 causes of deviations detected that the most important (46.1%) of those were related tofailure of equipment. ETBA method detected 10 types (24 sub-types) of energy so that the most important riskswere chemical and potential energies. ETBA detected 33 hazards that 37.79% of them were unacceptable andundesirable. Although HAZOP was more powerful than ETBA to predict and detect the hazards, butimplementation of ETBA is easier than HAZOP and it needs a short period of time. Also ETBA was able toreveal some hazards which couldn’t be considered by HAZOP. Therefore, combining of two methods is betterselection compared to either of them alone for risk assessment in process industries.

Key words: Process Industry Gasoline Refinery Safety Risk Assessment HAZOP ETBA

INTRODUCTION human errors, too much reliance on the safety of

Complexity and expanding of chemical and process face and cope with critical situations and lack of HSE rulesindustries leads to high safety risk and disaster in world. [4].Some of these tragic events were Feyzin, Mexico City, To prevent incidents, the safety experts mustBhopal (India), Piper Alpha (UK), explosion of liquid fuel recognize, assess and reduce or control the potentially(North Sea) or Chernobyl (Russia) [1]. small, big, visible and invisible hazards by using risk

Gasoline refinery industry is one of the most assessment and management techniques. The importanceimportant units in process plants and each deviation of risk assessment is to help the decision making forfrom desirable situation can result in a hazard. Each year, choosing the good solutions and for convincing thethe incidents deliver so many irreparable damages to managers to spend resources for safety solution. personnel and equipments that almost all of them are Several methods with some advantages andpredictable and preventable by risk assessment and disadvantages for risk assessment of hazard is includingcontrol strategies [2]. Risk is the harm or injury from a of the PHA, FMEA, LOPA, FTA, HAZOP and ETBA [5-6].hazard that will occur to specific individuals or groups Moreover, because of the multifaceted nature ofexposed to a hazard for every system or process [3]. workplaces, the use of single-oriented methods, such asAnalysis of incidents points to different factors such as AEA (man oriented), FMEA (system oriented), or HAZOP

machinery, problems in design of the plant, unprepared to

African J. Basic & Appl. Sci., 6 (1): 01-05, 2014

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(process oriented), is not satisfactory [7] and no single an effective method to detect hazard and systemone will always be the best [8]. Different techniques have operability problem by determination of their affects. been introduced for analysis of process systems withtheir own capabilities and limitations namely HAZOP and Implementation of HAZOP is as follows [9, 15-16]:ETBA [9].

HAZOP was developed since 1960 for analysis of Break the process down into functional nodes: Insafety risk factors and can be considered as one of the this research, the nodes were consist of; 1) frommost accurate methods for identifying hazards in the FRC-301 to ending of gasoline entrance pipelines, 2)various industries, especially chemical plants [10] and it’s tower-301 and floater, 3) from control valve-305 toa widely used process hazard analysis (PHA) approach caustic entrance pipelines into tower, 4) gasoline exit[11]. But HAZOP study is expensive due to highly time pipeline on top of the towerconsumption [10] and also requires the key personnel Identifying the deviations in every node usingaway from their daily jobs to attend the HAZOP meetings keywords:which might last for weeks [12]. On the other hand, inattention to existence of different energies in process Primary Keywords: pressure, temperature, flow, etc.plants including of chemical, electrical, mechanical and Secondary keywords: no, more than, less than, asthermal, some of researchers apply the ETBA for safety well as, etc.risk assessment. For example; Isomax unit in refinery [2], Estimating the possible causes and consequence ofchlorination unit in treatment plants [9], foundry industry deviations[13] and corn processing industry [14]. Identifying the existed safeguards and their

Gasoline refinery has high risk of potential hazards, effectivenesstherefore the aim of this study was to investigate the Determination of the hazards risk level safety risk in one of the Iranian gasoline refinery (nearing Define controls to reduce the riskthe residential area) by applying two methods of HAZOP Re-determination of the hazards risk level and ETBA and also the results of two techniques werecompared. ETBA (Energy Trace and Barrier Analysis) Technique:

MATERIALS AND METHODS identification of hazards by focusing on the existence of

At first, the primary method of risk assessment called"what if..?" has been used to recognize all of thepotentially hazard in process. The basis of this method isto pose some questions like "what will happen if…?" andthen find the right answer for these questions. Beforethat, we separated the process to smaller sections andthen the questions for each section are posed [15].

Data were gathered using the direct observation,process flow diagram (PFD), piping and instrumentdiagram (P and ID), interview with key persons andwalking-talking through Methods [9]. Finally the HAZOPand ETBA worksheets are accomplished. To performthese methods, the experts group should be formed [4]. Inthis study, a 7-member team was formed that consist of:the process, chemical, electrical, mechanical and safetyengineers in refinery unit and two safety experts(researchers). In following both of HAZOP and ETBAmethod have been explained:

HAZOP Technique: HAZOP is a qualitative, systematic,creative and group method that is so easy to learn and is

ETBA is a system-based analysis developed to

different energies in system. First, the system was definedin a way that enabled the analyst to identify and traceenergies from the time they enter the system until exitingthe system. The next step was to use the ETBA checklist,which included the energy types that might be in thesystem. Then one energy type was selected at a time andtraced through the system. Wherever a potentialunintended energy release or exchange was discovered,the people and/or objects that are likely to be affected bythe scenario were identified. [17]

Implementation of ETBA is as follows [2, 9, 13, 14 and17]:

Identifying the energy types (15 types and 68subtypes of energy).Determination of barriers in the energy pathwaysDetermination of vulnerable targets includingpersonnel, equipment, etc.Determination of hazards risk level and effectivenessof controlsDefinition of controls to reduce the riskRe-determination of hazards risk level


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Risk Level Analysis: The objective of risk level analysis One study in chlorination unit showed that 32.5% ofis to quantify the relative importance of each failure, so deviations had intolerable and moderate risk levels, sothat priorities for action to reduce the probability or that increasing the volume, pressure and temperature ofseverity of incidents [15]. Risk level is a combination of liquid chlorine in the cylinder had the highest risk levelsseverity of an effect (4 groups from catastrophic to [9]. In other study at chemical unit, 46.1% of deviationsmarginal) and the probability of occurrence (5 groups from were unacceptable and undesirable, so that the mainfrequent to rare). Determination of Hazard’s risk level has causes of hazard were equipment’s’ failure (43.5%) andbeen done based on Mil-Std-882E matrix in both HAZOP human error (35.8%) [18]. The main causes of deviationsand ETBA methods [13, 14, 18-20]. were failure of equipment and human error [21].

RESULTS AND DISCUSSION method differently detects the hazards based on process-

At first, 60 types of hazard and their consequences using this method even in the approximately samehas been detected by use of "what if..?" method, which process.used as basic information for risk assessment. Result ofrisk assessment by using of HAZOP and ETBA methods ETBA: 10 types and 24 subtypes of energy werehave been separately shown. detected that had a potential to damage the goals (man,

HAZOP: 44 deviations were identified, so that 11.37% of chemical (20.83%), potential (12.5%) and electrical (12.5%)deviations were not acceptable, 36.36% were undesirable, energies. 33 hazards were detected so that they were29.55% were acceptable but needed reconsideration and 10.52% unacceptable, 27.27% undesirable, 27.27%22.72% were acceptable and didn’t need any correction acceptable but needed reconsideration and 39.39%act. Also 126 possible causes of hazard are detected that acceptable and didn’t need any correction act. ETBA46.03%, 40.47%, 7.95% and 5.55% of them were related to worksheets have been filled for all of the 33 diagnosedfailure in equipment, failure in process function and deviations in process. For instance; one of thesecontrolling systems, human errors and condition of worksheets shows in Table 2.weather and the natural disasters respectively. In this study, 37.79% of risks were unacceptable

The main causes of hazard were consisting of: 1) and undesirable. In other studies; 57.6% of hazardsopening of bypass pathways, 2) dirty and obstruction of in chlorination unit [9], 70% of hazards in foundrypump's filter, 3) corrosion of the gasoline transmitter industry [13] and 68% of hazards in petrochemicalpipelines and the trays in tower, 4) rotation of gasket, 5) plant [22] had unacceptable and undesirable riskoutage of electrical power, 6) failure in alarms, 7) closure levels.of control valves, 8) failure in check valves, 9) increasing In present study, the most important risks werepressure in plant air and 10) failure in welding of pipelines. chemical, potential and electrical energies. The highestHAZOP worksheets have been filled for all of the 44 risk levels in different study using ETBA were related todiagnosed deviations in nods. For instance, one of these “The reaction and involvement of individuals” [9],worksheets shows in Table 1. “Potential energy” [13-14], “Rotational and linear kinetic

In this study, 47.73% of deviations were energies” [17] and “scaffolding and excavating” [22].unacceptable and undesirable and the most important These studies shows that ETBA method has expandedcauses of deviations (46.1%) were related to failure of application in process industries and in attention toequipment but the human errors weren’t so important. process-style detect the existing hazards.

The results of studies have shown that the HAZOP

style and it probably couldn’t be gained the same results

equipment and products). The main energies were

Table 1: HAZOP Worksheet: Operational node description; Desulphurization process at Tower-301

No. Guide Word Element Deviation Possible causes Consequences Safeguards Risk Level Required Actions Risk Level

1 Increase Flow Increase of feed flow -Opening of -Corrosion result in increased velocity -Installation of S.V A3 -pressure control system

bypass trace -Reduce of Desulphurization -Inspection of bypass pipeline C4

Table 2: ETBA Worksheet: Entrance pipelines to tower-301

NO. Type of Energy Description of Risk Exposure to potential targets Protection of the flow of energy Risk Level Regulatory actions and proposed Risk Level

1 Corrosive Fire due to leakage of People, equipment -Thickness Measurement -Cathodic protection of the pipelines

(Caustic and gasoline) flammable materials and product by gamma rays 3C -anti-corrosion materials 4D


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In this study, the main corrective actions was Pressure control system in tower-301.improvement of equipment, also in other studies wereimprovement and regular maintenance of equipment andusing of correct operational methods [6, 17].

The main detected hazards were consisting of:

Corrosion of the pipelines, tower’s body and traysdue to gasoline and caustic.Gasoline leakage due to rotation of gasket andloosening of flange Fire result in cranes’ or hammer mechanical beats andstatic electricityReaction between water and spilled caustic that ledto induce of hydrogen’s explosive vapor.Damage to dermal, ocular and respiration result ingasoline and caustic.Electrical shock result in connecting of bare wire tothe tower’s body.Tripping and Falling due to slippery surface.Pipeline explosion result in high pressure.Hearing loss because of pump and generator sound.

The main existing obstacles for reducing orpreventing from release of unwanted energies:

Metallic cover for electrical cable.Fuse, earth system and lightning arrester.Reticulated metallic guard in stairway.Pressure indicator.Ear protection equipment.Determination of the liquid thickness by gamma ray.Application of caustic as furnace fuel after theprimary use of that.

Comparing of HAZOP and ETBA Techniques: HAZOPmethod detected the existing risks both more number andmore severity than ETBA method. This depicts thatHAZOP is more precise than ETBA in identifying the risksat gasoline refinery process. Applying of ETBA is easierthan HAZOP. Also studies showed that ETBA hadexpanded application and acceptable sensitivity in hazarddetecting at process industries.

The HAZOP and ETBA techniques identified thedifferent hazards in same process and it seems that thesetwo techniques can be used as complement methods forrisk assessment especially in process industries.

Some corrective suggestions to decrease the risklevel of hazard were:

Regularly maintenance of the equipment, like: FRC,Check valves, etc.

Installation of PC (regulator) in feed transmissionpipelines.Cathode preservation or injection of the anticorrosivein tower and pipelines.Gas detector for detect of Hydrogen concentration.Safety alarms to prevention from crushing of vehiclesto pipelines.Ambulant guard on the control valves to protect fromstroke.Educational programs according to needs for all ofoperators periodically.Anti-spark rails in crane.Compensative pump for prevention of water pressureloss, if the existing pump be destroyed.Cooling system for prevention of rising temperature.Transmission of the refinery unit to a safe place (Farfrom the residential area).

CONCLUSION

HAZOP is a more appropriate than ETBA topredict and detect the hazards. But applying of ETBA iseasier than HAZOP. These techniques can recognize aspecial hazard, then because of high complexity andhazardous of chemical processes, it’s better to use thecombination of these two methods to precisely detect thehazards.

ACKNOWLEDGEMENTS

The authors are grateful to the Zanjan University ofMedical Sciences, Zanjan (Iran), for financial support.

CONFLICTS OF INTEREST: None declared.

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